Noun. Usually an open cup or jar on the counter, near the register. Patrons can tip the staff by adding cash to the jar, instead of leaving cash on the table or on the bar. Restaurant and bar servers might split the pot each shift, so everyone gets a fair share of the tips.

Tip jars are also common in virtual worlds that require virtual money for certain activities. They can take any shape or appearance, because they just need to run a transactional script (just like a credit card swipe). Users touch or click the virtual object to "leave a tip", and the owner of the tip jar gets paid immediately. In Second Life, tip jars are often left where visitors are likely to make donations. They are not always placed by the owner of the parcel or even with their permission, so the presence of a tip jar can be very deceptive. If the land is free to build on, someone is gonna leave a tip jar there, sooner or later - and some sucker is gonna click on it for no good reason (literally giving money away).

"I forgot to leave some money on the table."
"Don't worry about it. There's a tip jar."

"Rez your tip jar on the floor or somewhere beside you, don't attach it or wear it. Don't forget to take it back to your inventory before you logoff, otherwise the land owner will return it and it'll end up in the lost and found folder."